Editor’s note (4/2/2017): This week marks the 100-year anniversary of the U.S. entry into the First World War. Scientific American, founded in 1845, spent the war years covering the monumental innovations that changed the course of history, from the first tanks and aerial combat to the first widespread attacks with chemical weapons. To mark the centennial, we are republishing the article below and many others. For full access to our archival coverage of the Great War sign up for an All Access subscription today.